While there are guidelines in place on the amount and intensity of exercise you need to reap health benefits, the new research is the apparently the first to look at whether or not people actually know what those intensity levels feel like physically.

Scientists from York University in Toronto say they gathered 129 sedentary adults between 18 and 64 from Canada. The volunteers were given written exercise guidelines to study, then asked if they felt they could comply. Most participants said they could comply with the guidelines or were already in compliance with them.

Then, the scientists measured the subjects’ heart rate by having them walk and jog on a treadmill at three different paces they deemed light, moderate or vigorous. At the end, the volunteers were also asked to walk at a pace they felt was the least taxing but would still qualify as moderate in order to get the health benefits from it.

The results were surprising. Few people were actually achieving moderate exercise levels when they thought they were, and even fewer were working out vigorously when they believed they were.

What’s more, only 25% of those who’d thought they were still reaping benefits while exerting the least amount of effort were actually walking at a pace brisk enough to yield said benefits.

“The findings from this study suggest that the majority of young and middle-aged to old adults underestimate the intensity of PA [physical activity] that is required to attain health benefits,” researchers wrote. “Participants accurately estimated light effort PA and underestimated moderate and vigorous effort PA, and there appear to be no differences by sex, ethnicity or across BMI classifications in the understanding of the commonly used PA intensity descriptors.”

Just in case you were wondering, the guidelines say healthy adults should do 150 minutes of moderate or 75 minutes of vigorous exercise each week. A “moderate” pace means your pulse should increase to about 64 percent to 76 percent of your maximum heart rate. During “vigorous” exercise, your pulse should be between around 77 percent and 90 percent of your max.